Abstract

Metastable β‐tungsten was identified, using transmission electron microscopy, in arrays of low pressure chemical vapor deposited contacts on patterned silicon wafers. In contrast, only α‐tungsten was found in filmsdeposited onto bare silicon wafers under identical conditions. Thus, we have shown that contact wells etched through oxide can play a role in determining which tungsten phase is deposited by low pressurechemical vapor deposition. This effect was observed for a variety of furnace conditions (T=300–330 °C, H2/WF6=150:1–400:1). Transmission electron micrographs and selected area diffraction patterns are presented which illustrate the microstructural differences between the α‐ and β‐tungsten phases. Possible sources of oxygen or fluorine, impurities which are believed to stabilize β‐tungsten, are discussed and related to the geometry of the vias cut through oxide on patterned wafers.